So,
Slack & Gitter didn’t work, the “community chat thread” on this forum is all crickets and tumbleweeds, but we had a reasonably active IRC channel going on at one point in the past. It worked. It was #nupic on freenode.
While that channel technically still exists it’s full of dead bodies and nothing else, and I never liked the name anyway. NuPIC is a tool. HTM is the purpose. So I started a new channel, still on IRC freenode, called ##htm. Note the two hashes. All join.
Be aware that IRC is pretty much the wild west of the internet. There are no rules. This has advantages and disadvantages. If you prefer “safe spaces” and “gated communities” then this forum is maybe better suited for you.
Cheers.
– Rik